| 摘要 |
A planetary gear set comprises a plurality of pinions P1, P2 meshing with a sun gear, and a carrier C that shaft-supports the pinions. The carrier has an annular peripheral wall 12 that extends entirely around outer peripheries of the plurality of pinions. Thin-wall portions 12a receded at a radially inner side are formed in the annular peripheral wall, at circumferential-direction positions corresponding to the positions of the pinions. The circumferential continuity of the annular peripheral wall secures a carrier rigidity. The formation of the thin-wall portions avoids interference between each pinion and the annular peripheral wall without involving an increased diameter of the carrier. The pinions P1 have a smaller diameter than the pinions P2. A platy wall portion 32 of a bridge portion 3 extends in the direction of a circumference of the carrier, outwardly of the pinions P1. Therefore, rigidity and strength allowing arrangement of many gear pairs can be achieved, and the durability of the planetary gear will improve due to a reduced load per gear pair.
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